Complex aluminum greases of enhanced stability



United States Patent Int. Cl. C10m 5/16 U.S. Cl. 252-36 6 Claims Thisinvention concerns novel improved grease compositions having as theirgrease thickener aluminum carboxylate salts. More particularly, thisinvention concerns novel grease compositions having enhanced stabilitycomprising novel grease compositions having aluminum carboxylate saltsas grease thickeners and alkali meta aroates as stabilizers. 1

Complex aluminum carboxylate greases are well known in the art and havebeen reported in numerous patents (see U.S. Pat. Nos. 2,768,138,2,719,826, 2,654,710 and 2,599,553). The aluminum soap thickeners aredescribed as having at least 2 dissimilar substantiallyhydrocarbonaceous organic anions having certain characteristics. Theorganic anions are generally oleophilic; however, one of the organoanions of the complex soap molecule has a greater oil solubility thanthe other organo anion of the same soap molecule. Further on, thealuminum di soaps are described as the aluminum di-soaps of the moresoluble organo-anions (i.e., the relatively oleophilic anions) aresoluble in an amount of at least 5 percent (by volume) at 400 F. inpetroleum white oil having viscosity characteristics 'of 346 SSU at 100F. and 54 SSU at 210 F. and having a viscosity index of 92. That is, at400 F., 5 percent of the aluminum soap of the oleophilic organo anionwill form a true solution in the petroleum white oil.

On the other hand, the aluminum soaps of the less soluble organo anions(i.e., the relatively oleophobic anions) are soluble in the above whiteoil in an amount of less thanl percent at 400 F. That is, at 400 F. lessthan 1 percent (from 0 percent to about 1 percent) [by volume] of thealuminum soap containing the oleophobic anions will dissolve in thewhite oil to form a true solution.

The carboxylic acids from which the oleophilic anions are derived areillustrated by caprylic acid, capric acid, lauric acid, myristic acid,palmitic acid, stearic acid, l2-hydroxystearic acid, arachidic acid,melissic acid, oleic acid, linoleic acid, etc. The preferred acids arestearic acid and hydroxystearic acid. The preferred carboxylic acidshave from 14 to 22 carbon atoms, more usually from 16 to 18 carbonatoms.

The relatively oleophobic anions are substantially hydrocarbon instructure, are from about 7 to 12 carbon atoms and have an aromatichydrocarbon ring (benzene). Illustrative of such acids are benzoic acid,toluic acid, ethylbenzoic acid, phenylacetic acid, phenylpropionic acid,salicyclic acid, etc. The preferred acids are those of from 7 to' 9carbon atoms having the carboxyl group bonded to the benzene ring, e.g.,benzoic acid, toluic acid, dimethylbenzoic acid, and ethylbenzoic acid.

While any of the methods of preparation disclosed in the various patentsindicated above might be used, a preferred method of preparation isdisclosed in copending application Koundakjian and Dreher, Ser. No.331,127, filed Dec. 17, 1963, now U.S. Pat. No. 3,345,291. Accordingly,approximately 1.5 to 2.5 molar parts of the oleophilic acid andoleophobic acid, in which the mole ratio of the oleophilic acid to theoleophobic acid is in the range of from about 0.25 :1 to 4: 1,approximately 1 molar part of a lower aluminum alcoholate, from 0 to 1.5molar parts of water and a large molar excess 3,511,781 Patented May 12,1970 "ice of an oil of lubricating viscosity are heated to a temperaturein the range of about 150'to 300 F., until reaction of the alcoholatewith the acids is substantially complete, then a quantity of water isadded in the range of 0.05 to 10 molar parts and at least suflicient tobring the total water introduced to at least about 0.5 molar part, andthe resultant mixture is vigorously agitated at a temperature of fromabout 200 to 500 F. The grease is then ready to be used.

It is found, however, that after long periods of time, particularly atelevated temperatures, the grease begins to liquefy. In attempting tostabilize the grease, many of the known commercial stabilizing agentsare found to be ineffective or have detrimental side eifects,particularly in the presence of common additives, such as the filler,zinc oxide, or the common rust inhibitor, sodium nitrite.

Pursuant to this invention, alkali metal aroates (aromatic carboxylicacids)-the alkali metal is of atomic number 3 to 19, preferably 11(sodium) and the aroate is of from 7 to 12 carbons, preferably benzoicacid-are added in from about 0.1 to 20 weight percent, more usually 2 to7 weight percent to the complex aluminum grease composition to provide acomposition with enhanced stability at elevatedtemperatures. The alkalimetal aroate may be added during the preparation of the grease orsubsequent to its preparation.

The basic complex aluminum soap may be described by the general formula:

0 (O-iL-R):

in which R is an aliphatic group having 8 to about 30 carbon atoms, Aris an aromatic radical, preferably a monocyclic hydrocarbon radical, Ris either hydrogen or a lower aliphatic hydrocarbon radical, at leastone-half of R being hydrogen, x is at least 0.25, y is at least 0.25,the sum ofx and y is from 1.5 to 2.5, and z is from 0.5 to 1.5. Thealuminum is trivalent in the. above formula and, therefore, the sum ofx, y and z is 3. However, this formula is not intended to indicate theactual structure of the aluminum salt in the grease, but ratherindicates the stoichiometry between the aluminum cation and the anions.

Illustrative of R, which is derived from the lower alcoholates used, aremethyl, ethyl, propyl, isopropyl, butyl, or mixtures thereof, namelyalkyl groups of from 1 to 6 carbon atoms.

The oil component of the grease is a hydrocarbon oil of lubricatingviscosity derived from petroleum or synthesized. Description of thevarious oils is found in U.S. Pat. No. 2,768,138. These oils may bemixed base, naphthenic based, asphaltic based or paraflin based. Thesynthetic oils may be derived by the polymerization of ethylene,propylene, isobutylene, or other hydrocarbon olefin to an oil of thedesired viscosity.

As indicated, the alkali metal aroate may be added together with thealuminum alcoholate and fatty acids or may be added to the alreadyprepared grease.

The following example is offered by way of illustration and not by wayof limitation.

EXAMPLE 1 A 1,600 pound batch of grease was prepared by the process ofthis invention. The components of the batch were 64.8 pounds stearicacid, 36.2 pounds of benzoic acid, 53.1 pounds of aluminum isopropoxide,1,320 pounds of white oil, pounds of sodium benzoate, 32 pounds of zincoxide, 8 pounds of sodium nitrite and 6.2 pounds of water.

he stearic acid, benzoic acid and 150 gallons of e oil were charged to amixer and heated to 220 F. agitation. After the acids were dissolved,the soluwas circulated from the mixer to a Charlotte mill back to themixer. The aluminum isopropoxide was d to the mixer over a 30-minuteperiod while agitain the mixer was maintained and circulation of the urethrough the Charlotte mill was maintained. The llatlOIl and agitationwere continued for 45 minutes the temperature was maintained at 210-220F. he end of 45 minutes, 6.2 pounds of water were d and the resultantmixture was slowly heated to F. During the heating the materials in themixer 1 agitated, but circulation through the mill was disinued. Afterthe temperature of 320 was reached roximately 1 hour), the reactionmixture was slowly at with continuing agitation to 230 F. During the ngthe remainder of the white oil was added. When temperature of 230 F. wasreached, the sodium 1e mixed with 3 gallons of water was added to theion mixture which was then reheated to 260 F. held at that temperaturefor about 30 minutes to drate the reaction mixture. The reaction mixturethen cooled to 200 F. and the sodium benzoate and zinc oxide added. Theresultant mixture was cired-through the Charlotte mill and slowly cooledto F. When the temperature reached 160' F., it was lrawn from themixture and passed through a filter n and packaged. hile more or lessoil may be used, in general, satisry greases are obtained when the soapcontent of grease is in the range of about 4 to 16 weight perllowing theprocedure of Example 1, greases having ng weight percents of thealuminum salts were pre- I. Also varied, was the method of introductionof odium benzoate. These greases were tested accordo the Thin Film LifeTest at 250 F., both in the :nce andabsence of other additives.

TABLE 1 a n o :o

said oil to a grease, a compound of the formula:

carbon atoms, R is selected from the group consisting of hydrogen and alower aliphatic hydrocarbon radical, at

10 least one-half of R being hydrogen, and Ar is an aromatic hydrocarbonof from 6 to 11 carbon atoms, at is at least 0.25, y is at least 0.25,the sum of x and y is from 1.5 to 2.5, z is from 0.5 to 1.5, and the sumof x, y and z is 3, and

alkali metal aroate of from 7 to 12 carbons, wherein said metal is ofatomic number 3-19.

2. A composition according to claim 1, wherein said alkali metal is ofatomic number 11.

3. A composition according to claim 1, wherein said alkali metal is ofatomic number .11 and said alkali metal aroate is present in an amountof from about 0.1 to 10 weight percent of said composition.

4. A composition according to claim 1, wherein said alkali metal is ofatomic number 11 and said alkali metal aroate is present in amount ofabout 5 weight percent of said composition.

5. A lubricating oil composition comprising an oil of 30 lubricatingviscosity and in an amount suflicient to thicken said oil to a grease, acompound-of the formula:

gen and methoxy, at least one-half of R being hydrogen,

E F o H I (Amounts are reported as weight percent) mass A 100 95 97aluminum benzoats stearate hydroxide in white 011 having 468 SUS at 100F. and 62 BUS at 210 F. aluminum benzoate steer-ate hydroxide in white011 having 466 SUS at 100 F. and 62 SUS at 210 F.

um benzoate milled into the grease with Three Roll Mill lium benozateadded as water solution and water then removed by heating.

is evident from the above table that a great extenx is at least 0.25, yis at least 0.25, the sum of x and y of useful life is obtained by theaddition of sodium ateas exemplary of alkali metal aroatesto the inumcomplex greases. Not only is this evident with Iasic grease itself, butmore important, it is also at in the presence of common commercialadditives ently added to-greases. Sodium benzoate finds paruse for thosegreases used in machines in propinof food. These greases which generallyemploy oil, sodiunrnitrite as their rust inhibitor and zinc as a fillerand colorant, are greatly improved in useful life by the addition ofsmall amounts of m benzoate.

will be evident to those skilled in the art, various fications on thisinvention can be made or followed, e light of the foregoing disclosureand discussion, rut departing from the spirit or scope of the disre' orfrom the scope of the following claims. laim: A lubricating oilcomposition comprising an oil of eating viscosity and in an amountsuflicient to thicken is from 1.5 to 2.5, z is from 0.5 to 1.5 and thesum of x, y andz is 3, and

in an amount suflicient to provide stabilization sodium benzoate.

6. A composition according to claim 5, wherein said sodium benzoate ispresent in an amount of from about 5 weight percent of said composition.

References Cited UNITED STATES 1 PATENTS 2,182,137 12/1939 Ricketts 252--41 2,431,760 12/1941 Licata 252-36 2,599,553 6/1952 Hotten 2s2 35 0DANIEL E. WYMAN, Primary Examiner C. F. DEES, Assistant Examiner U.S.Cl. X.R.

in an amount suflicient to provide stabilization an

1. A LUBRICATING OIL COMPOSITION COMPRISING AN OIL OF LUBRICATINGVISCOSITY AND IN AN AMOUNT SUFFICIENT TO THICKEN SAID OIL TO A GREASE, ACOMPOUND OF THE FORMULA: